Calculate time difference between two events (given date and time) in R

I'm currently struggling with a beginner's issue regarding the calculation of a time difference between two events.

I want to take a column consisting of date and time (both values in one column) into consideration and calculate a time difference with the value of the previous/next row with the same ID (A or B in this example).

ID = c("A", "A", "B", "B")
time = c("08.09.2014 10:34","12.09.2014 09:33","13.08.2014 15:52","11.09.2014 02:30")
d = data.frame(ID,time)

My desired output is in the format Hours:Minutes

time difference = c("94:59","94:59","682:38","682:38")

The format Days:Hours:Minutes or anything similar would also work, as long as it could be conveniently implemented. I am flexible regarding the format of the output, the above is just an idea that crossed my mind.

For each single ID, I always have two rows (in the example 2xA and 2xB). I don't have a convincing idea how to avoid the repition of the difference.

I've tried some examples before, which I found on stackoverflow. Most of them used POSIXt and strptime. However, I didn't manage to apply those ideas to my data set.

Solution

Here's my attempt using dplyr

library(dplyr)
d %>%
  mutate(time = as.POSIXct(time, format = "%d.%m.%Y %H:%M")) %>%
  group_by(ID) %>%
  mutate(diff = paste0(gsub("[.].*", "", diff(time)*24), ":",
                       round(as.numeric(gsub(".*[.]", ".", diff(time)*24))*60)))


# Source: local data frame [4 x 3]
# Groups: ID
# 
#   ID                time   diff
# 1  A 2014-09-08 10:34:00  94:59
# 2  A 2014-09-12 09:33:00  94:59
# 3  B 2014-08-13 15:52:00 682:38
# 4  B 2014-09-11 02:30:00 682:38